Automotive vehicle suspension dampers, better known as "shock absorbers", and dampers in other suspension systems are basic hydraulic devices which convert mechanical motion energy into thermal energy. In so doing, they control suspended mass oscillations to preclude build-up to untenable levels. Many applications of these devices, particularly automotive, provide extremely restrictive package sizes and locations for the amounts of energy to be handled. As a result, the units tend to overheat. This causes premature seal failures, fluid degradation, structural softening and general system deterioration.
Until recently, operation of military equipment in the same "throw-away" mode as the commercial automotive market was acceptable. Dampers were not excessively expensive, were usually not mission-critical and were generally easy and cheap to replace. With the advent of high performance, cross-country vehicles, this situation has changed. The dampers in these systems are critical to overall vehicle performance. Coupled with their increasing criticallity is their increased cost. "Throw-away" is rapidly becoming unacceptable. System failure is not allowable as it could put in jeopardy the vehicle, its crew and the mission. Thus, a means of preventing overheat failures is now necessary.
Several factors dictate the chosen approach. The system must be self-actuating, preferably self-contained and inherently simple. Once the overload condition has passed, the unit should reset itself without outside aid. Also addressed are ways to keep the system from thermally overloading in the first place. These involve methods for increaasing cooling area, improving heat transfer and distributing heat load.